1. Field of the Invention
The present invention relates to a swash plate type compressor adapted for use in compressing a refrigerant of a vehicle air-conditioning system, and more particularly, it relates to an improved internal sealing of the swash plate type compressor.
2. Description of the Related Art
A swash plate type compressor for use in a vehicle air-conditioning system is known. A typical swash plate type compressor is disclosed in, for example, U.S. Pat. Nos. 4,070,136 and 4,403,921 to the same assignee of the present application. The typical swash plate type compressor has front and rear cylinder blocks axially combined together, front and rear housings connected to the front and rear ends of the combined cylinder blocks, via front and rear valve plates, and a rotatable drive shaft arranged so as to be axially extended through the front housing and the combined cylinder blocks, and having thereon a swash plate. The front and rear cylinder blocks, the front and rear housings, and the valve plates are axially and tightly combined together by a plurality of long screw bolts. In the swash plate type compressor, when a refrigerant returns from the air-conditioning circuit, via a return piping, it is introduced into suction chambers formed in the front and rear housings while passing through a suction port, a swash plate chamber, and inlet passageways of the combined cylinder blocks. The refrigerant is subsequently pumped into cylinder bores formed in the combined cylinder blocks while suction valves are opened in response to the reciprocation of double headed pistons within the cylinder bores. The pistons are operatively connected to the swash plate rotatable with the drive shaft, and compress the refrigerant within the cylinder bores. The compressed refrigerant is pumped from the cylinder bores into exhaust chambers formed in the front and rear housing while delivery valves are opened in response to another reciprocation of the double-headed pistons. The compressed refrigerant is subsequently delivered from the exhaust chambers toward an outlet port of the compressor, through delivery passageways and is then sent to the air-conditioning circuit. Thus, each of the front and rear housings of the compressor has a low pressure suction chamber and a high pressure exhaust chamber, respectively. At this stage, the conventional swash plate type compressor has one of two different arrangements of the suction and exhaust chambers in the housings, i.e., the suction chamber is arranged inside the exhaust chamber within the respective housing, or the suction chamber is arranged outside the exhaust chamber within the respective housing. With the former arrangement, there is an advantage such that, since a drive shaft sealing portion located adjacent to the low pressure suction chamber of the front housing need not be isolated from the suction chamber, the internal construction of the front housing can be simplified. Japanese Examined patent publication No. 56-27710 discloses a six-cylinder swash plate type compressor employing the above-mentioned former arrangement of the suction and exhaust chambers. In the compressor of this Patent publication, the suction and exhaust chambers are simply formed in inner and outer annular chambers separated from one another by a circular separation wall.
The present inventors contrived to increase the number of cylinder bores of the compressor of the Japanese Examined patent publication No. 56-27710. That is, they designed and manufactured a ten-cylinder (five at the front and five at the rear) swash plate type compressor having an internal construction similar to the compressor of this patent publication. In that case, as shown in FIG. 4, a front housing 4 was formed with a substantially pentagonal-shape inner annular suction chamber 12, and an outer annular exhaust chamber 11 isolated from the inner suction chamber 12 by a non-circular curved separation wall 13. This formation of the pentagonal suction chamber 12 is due to the necessity for arranging bosses in which five through-bores 14 are formed to enable the insertion therethrough of the long screw bolts combining the cylinder blocks and the housings, and the need for five suction apertures 15 in the valve plate to enable a suction therethrough of refrigerant from the suction chamber 12 into the five cylinder bores 10. However, the front housing 4 shown in FIG. 4 must suffer from the following defect. That is, when the refrigerant is compressed within the cylinder bores 10, a valve plate (not shown in FIG. 4) arranged between the front cylinder block and the front housing 4 is subjected to a high pressure by the compressed refrigerant, and as a result, the central portion of the valve plate, i.e., the portion facing the suction chamber 12 of the front housing which is less influenced by the clamping force of the screw bolts inserted in the through-bores 14, is forcedly deformed in a direction separating it from the front cylinder block. Further, with the central portion of the valve plate, the deformation occurring at portions remote from the separation wall 13 is larger than that occurring at the remaining portion. This is because the separation wall 13 per se effectively suppresses the deformation of the above-mentioned remaining portions of the valve plate. At this stage, since inlet passageways 18 for communicating between the suction chamber 12 and a swash plate chamber (not shown in FIG. 4) are provided in the front cylinder block so as to be located between the two neighbouring cylinder bores 10, the location of the inlet passageways 18 is very close to the above-mentioned large deformation portions of the valve plate. Therefore, when such deformation of the valve plate occurs, a breakage of the sealing occurs between the cylinder bores 10 and the inlet passageways 18. As a result, the high pressure refrigerant compressed within the cylinder bores 10 is easily and directly diverted into the inlet passageways 18 by passing through a short gap s caused by the breakage of the sealing, and heat is applied to the refrigerant prior to compression. This lowers the compression efficiency of the compressor, and accordingly, the refrigerating efficiency of the air-conditioning system.